Jianxun Dai

Excellent Humidity Sensor Based on LiCl Loaded Hierarchically Porous Polymeric Microspheres

A catalyst-free Friedel-Crafts alkylation reaction has been developed to synthesize hierarchically porous polymeric microspheres (HPPMs) with phloroglucin and dimethoxymethane. HPPMs with uniform size were obtained and the size can be tuned by the concentration of raw materials. The chemical structure and hierarchical porous characteristic of HPPMs were characterized in detail. HPPMs were then loaded with humidity sensitive material LiCl to construct composites for humidity sensor. The optimum sensor based on 3 wt % LiCl-loaded HPPMs shows high sensitivity at the relative humidity (RH) atmosphere of 11-95%, small hysteresis, enhanced durability and rapid response. The sensitive mechanism was discussed through the investigation of complex impedance plots.

Drawn on Paper: A Reproducible Humidity Sensitive Device by Handwriting

This article describes the development of a kind of full carbon-based humidity sensor fabricated on the paper substrate by handwriting. The electrodes were written by commercial pencils, and the sensitive layer was drawn with an oxidized multiwalled carbon nanotubes (o-MWCNTs) ink marker. The resultant devices exhibit good reproducibility and stability during the dynamic measurement. The response of the optimized paper-based sensor exhibits about five times higher than sensors fabricated on the ceramic substrate, which is owing to the hydrophilic property of the paper substrate. The structure of the sensitive layer formed by dispersing sensitive materials in the porous surface of paper substrates alleviates the inner stress in the process of bending. The response of printing paper-based sensors only shows the 6.7% decay even under an extremely high bending degree.